VLSI-based system for durable high-density information storage

ABSTRACT

The invention relates to using VLSI techniques to store information on a substrate. One embodiment of a die with text deposited upon the die uses semiconductor processing techniques during fabrication. Included in the die are a substrate, a first paragraph and a second paragraph. The first and second paragraphs are in contact with the substrate. The second paragraph is aligned with the first paragraph in a column.

This application is a continuation of Ser. No. 09/662,300 filed Sep. 15,2000 now U.S. Pat. No. 6,680,162, which is a non-provisional of U.S.Provisional Patent Application No. 60/154,401 filed Sep. 17, 1999 bothof which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

This invention relates in general to VLSI fabrication techniques and,more specifically, to using these techniques to store information.

Any unnecessary traces of a metal, an oxide or a polysemiconductor areavoided in semiconductor processing. Adding unnecessary traces makes themask and fabrication more complex. This added complexity can increasethe likelihood of defects in the finished semiconductor circuit.Consequently, semiconductor circuits avoid use of unnecessary traces.

Progress in VLSI technology over the past few decades has beenphenomenal. Packing densities have increased by several orders ofmagnitude. However, to date, VLSI technology has been used largely forcreating electronic circuits, micro-machines or sensors. Other uses forthe VLSI technology are needed.

SUMMARY OF THE INVENTION

The invention relates to using VLSI techniques to store information on asubstrate. One embodiment of a die with text deposited upon the die usessemiconductor processing techniques during fabrication. Included in thedie are a substrate, a first paragraph and a second paragraph. The firstand second paragraphs are in contact with the substrate. The secondparagraph is aligned with the first paragraph in a column.

Reference to the remaining portions of the specification, including thedrawings and claims, will realize other features and advantages of thepresent invention. Further features and advantages of the presentinvention, as well as the structure and operation of various embodimentsof the present invention, are described in detail below with respect tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of an embodiment of a wafer having multiple die;

FIG. 2 is a depiction of an embodiment of a die from the wafer;

FIG. 3 is an illustration of an embodiment of a portion of a column fromthe die

FIG. 4 is an illustration of an embodiment of a word having diffractiongratings;

FIG. 5 is a flow diagram of an embodiment of a process for convertingtext and graphics into an electronic mask file;

FIG. 6 is a flow diagram of another embodiment of a process forconverting text and graphics into an electronic mask file;

FIG. 7 is a depiction of an embodiment of an upper case “A” element;

FIG. 8 is a depiction of the embodiment of the upper case “A” elementshowing constituent rectangle primitives;

FIG. 9 is a depiction of an embodiment of a lower case “a” element;

FIG. 10 is a depiction of an embodiment of a upper case “A” element withreverse contrast;

FIG. 11 is a depiction of an embodiment of a lower case “a” element withreverse contrast;

FIG. 12 is a flow diagram of an embodiment of a process forlithographing text and/or graphics onto a semiconductor substrate;

FIG. 13 is a side elevational view of an embodiment of a semiconductorwafer with text and/or graphics lithographed thereon;

FIG. 14 is a flow diagram of another embodiment of a process forlithographing text and/or graphics onto a semiconductor substrate;

FIG. 15 is a side elevational view of another embodiment of asemiconductor wafer with text and/or graphics lithographed thereon;

FIG. 16 is a flow diagram of yet another embodiment of a process forlithographing text and/or graphics onto a semiconductor substrate; and

FIG. 17 is a side elevational view of yet another embodiment of asemiconductor wafer with text and/or graphics lithographed thereon.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The present invention includes a novel use of Very Large ScaleIntegration (VLSI) technology for creating very durable and long-termrepositories of textual and graphical information. The invention allowsconverting the information to be stored into an input form suitable forVLSI fabrication systems, allows fabricating the informationrepositories and allows accessing the stored information. The inventioncreates features representing textual and/or graphical information on asemiconductor (or other) wafer. These features may be created on thewafer surface itself or on a layer of material deposited on the wafersurface. Such materials can include, but are not limited to, metals,oxides and photoresists. In this way, large amounts of text are archivedusing VLSI technology.

In the Figures, similar components and/or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Referring first to FIG. 1, a depiction of an embodiment of a wafer 100having multiple die 104 is shown. The die 104 are generally aligned in agrid across the wafer 100. Typically, all die 104 on the wafer 100 arethe same. Although the die 104 in this embodiment is rectangular, otherembodiments could have die of different shapes. For example, the diecould be shaped as star or cross.

With reference to FIG. 2, a depiction of an embodiment of a die 104 fromthe wafer 100 is shown. Approximately eleven columns 204 of text appearon the die 104. Each column 204 includes a number of paragraphs. Eachparagraph is separated by a hard return and a tab. In some cases thefirst character of a section or chapter is enlarged and/or ornatelydecorated to signify changing sections or chapters. A dark silhouettepattern 208 against a lighter background overlays the columns 204 oftext. The silhouette pattern 208 is darker than the background in thisembodiment, but other embodiments could reverse this. Although thisembodiment shows an English character set, other embodiments couldinclude character sets in any language as well as symbol character sets.

The features, once created on the wafer, can be overlaid with anoptically clear protective coating using materials such as a resin, anoptically clear overcoat (e.g., EXP980024 available from Brewer Science™of Missouri), a thin and clear nitrite film, a spin-on glass film, or analuminum oxide layer. Additionally, the back surface of the wafer can bemetallized to add durability to the typically fragile wafer 100.

Referring next to FIG. 3, an illustration of an embodiment of a portion212 of a column 204 from the die 104 is shown. The portion 212 is amagnification of a part of FIG. 2 that shows a test sample of text 308.The portion 212 shows the dividing line 316 between the silhouette 208and the background 312. To allow for contrast, the text 308 on thesilhouette 208 is a light color and the text 308 on the background 312is a dark color.

With reference to FIG. 4, an illustration of an embodiment of a word 400having diffraction grating subpattern is shown. By adjusting the spacingof the diffraction gratings, the word 400 or character appears indifferent colors. The minimum size of the features is limited only bythe capabilities of the VLSI fabrication technology used. For example,one-hundred and thirty nanometer features are being used today. Inaddition to colors, other embodiments could use bolding, underlining,italics, strikeout, subscripts, superscripts, shadows, small caps andother effects with the text 308. Further, the diffraction lines theproduce the different colors could be oriented at any angle with respectto the text 308 and not just horizontally as depicted in thisembodiment.

Referring next to FIG. 5, a flow diagram of an embodiment of a processfor converting text and graphics into an electronic mask file is shown.The process begins in step 515 where a text file 505 and graphics file510 are chosen and loaded into page layout software. The text 505 is ina file format such ASCII text or rich text. Included in the text file505 are hard returns between paragraphs and markers for the beginning ofa section or chapter. The graphics file 510 is preferably a two colorsilhouette.

Page layout software such as Adobe PageMaker™ or Quark Xpress™ is usedto create and lay-out the text and graphics in a space proportional insize to the dimensions of the desired die 104. The resolution of thedrawing in the page layout software is chosen such that it correspondsto the feature size of the semiconductor process. The number of columnsneeded and font size for adequate resolution is chosen with the pagelayout software. A page layout file 520 is produced from the software instep 515.

In step 525, the page layout file 520 is converted into a binary imagefile 530. This can be done using a screen capture program and an imagemanipulation program such as Hijaak Pro™ or Adobe PhotoShop™.Alternatively, custom software could perform this conversion to thebinary image file 530. In this embodiment, each pixel in the binaryimage corresponds to a rectangle in the die layout.

In step 535, the text and graphical regions of binary image file 530 arerepresented as a collection of simple geometric primitives in ageometric primitives file 540 that can be fabricated with the availablefabrication technology. Primitives such as rectangles are used in thisembodiment to represent each pixel, but in other embodiments can alsoinclude general polygons, triangles, lines, curves, and circles. Inalternative embodiments, several like and adjacent pixels can be groupedinto larger primitives.

In addition to a binary image file, diffraction patterns and colormaterials, for example, could be used to change the color of a graphicalimage. Some embodiments could change the processing materials to suitthe desired colors of the graphical image. Alternatively, colors in thegraphical image could signify a different shaped primitive (e.g., acircle) or signify a different style.

In step 545, each geometric primitive in the file 540 is translated intoa basic chip layout command such as a “Box” command (corresponding torectangles) in the CIF language to produce a CIF or GDS file 550. Inaddition to the CIF and GIF format, any other chip layout format couldbe used. The complete collection of primitives corresponding to thewhole binary file would, by this process, result in a list of “Box”-likecommands. It is noted, we use the phrase ‘box command’ to mean any of avariety of commands corresponding to simple geometric primitives in therest of this document. This list constitutes the chip layout file, whichcan be used by a VLSI fabrication facility to create the patterns forthe masks used in lithographing the die 104.

With reference to FIG. 6, a flow diagram of another embodiment of aprocess for converting text and graphics into an electronic mask file isshown. The process begins in step 610 where for each of the elements(e.g. letters of the alphabet, punctuation marks, numerals, and graphiccharacters) a binary pattern that represents that character is generatedfor a particular font in a font/style file 600. All these binarypatterns are collected into one or more ‘font/style files’. For eachelement of the font/style files 600, a list of primitives that make theelement is generated. This yields a “subroutine” for generating thatelement.

The list of primitives that make up an element can be generated in avariety of ways. In one embodiment, each pixel of the element is treatedas a separate rectangular primitive. The primitives generated from thefont/style file 600 are stored in a character subroutine file 630. Someembodiments may include special features in the character subroutinefile 630 such as printing a special character at the beginning of achapter or section. At this point in the process, the text can beprocessed to produce characters in the desired font.

A text file 620, the character subroutines file 630 and a binary imagefile 640 are loaded into the chip layout generator in step 650 toproduce a chip layout file 660. In this embodiment, the text file is anASCII file and the binary image file is a TIFF file. If only a text file620 is specified without a binary image file 640, each element in thetext file 620 is read and corresponding subroutine from the charactersubroutine file 630 is looked-up. The sequence of elements is translatedinto the corresponding sequence of subroutine calls and a chip layoutfile is created. The set of subroutine calls may be appended to thesubroutines.

If only a binary image or graphics file 640 is specified without a textfile 620, each pixel in the graphics file 640 is read and translatedinto an appropriate ‘box’ command. These ‘box’ commands form a chiplayout file 660.

In some instances, a graphics file 640 may be combined with a text file620 to create a chip layout file 660. There are several options foraccomplishing this. One option is to have the text wrap around thegraphics. The graphic itself is represented as a collection of geometricprimitives like rectangles. By knowing the position of the graphics, thetext can be wrapped around the graphics.

Another option is to have the text overlay the graphic, but to have thetext change polarity (normal or reverse contrast) depending on whetherit is inside or outside the graphic element. The text may changefeatures other than polarity. For instance, it could change style(normal or bold), change fonts (e.g. Geneva to Helvetica), or changefrom one type of element to another. Once the style or type of elementis determined from both the graphics and text file, the appropriatesubroutine is looked up from set of subroutines generated in thecharacter subroutine file 630 and outputted to the chip layout file 660.

The mask corresponding to the chip layout file 660 described above(e.g., CIF or GDS format) can be created using E-Beam Lithography, X-RayLithography, or any of a variety of techniques commonly used now or inthe future for VLSI. The input to the process is the chip layout file660 and the polarity of the mask. The mask can be a 1-to-1 contact maskor a minification mask suitable for use in a stepper configuration.

Referring next to FIG. 7, a depiction of an embodiment of an upper case“A” element 700 is shown. The element 700 approximates the fontHelvetica using a number of rectangles. Other embodiments could useother fonts. The black regions denote “pixels” of the element.Similarly, FIG. 9 shows a depiction of an embodiment of a lower case “a”element 900.

With reference to FIG. 8, a depiction of the embodiment of the uppercase “A” element 700 showing constituent rectangle primitives 800 isshown. The primitives 800 are rectangles of different sizes positionedto approximate the element 700. Each primitive is comprised of “box”commands each being a square defined by the feature size of the process.Some embodiments are not limited by the feature size of the process.Since the die is not a functional circuit, the only limitation on sizeand shape is defined by the state of the art in mask fabrication.Although this embodiment uses rectangular primitives, other embodimentscould have primitives of any geometric shape.

Referring next to FIGS. 10 and 11, shown are depictions of embodimentsof an upper case “A” and a lower case “a” elements 1000, 1100 withreverse contrast. Reverse contrast provides contrast for text overlayinga dark background or a dark silhouette.

With reference to FIG. 12, a flow diagram of an embodiment of a processfor lithographing text and/or graphics onto a semiconductor substrate isshown. A variety of methods can be used for fabricating chips 104 basedon mask described above. The process begins in step 1200 by depositingphotoresist directly on the wafer or on a layer of some other materialthat has first been deposited on the wafer. Next, expose the photoresistto electromagnetic radiation of the appropriate wavelength through themask in step 1210. Etch away the exposed or unexposed photoresist toleave a positive or negative impression and bake the photoresist toincrease its durability in step 1220. Optionally, the wafer is coatedwith an optically clear protective material.

Referring next to FIG. 13, a side elevational view of an embodiment of asemiconductor wafer 1300 with text and/or graphics lithographed thereonis shown. To produce the semiconductor wafer 1300 depicted; the processof FIG. 12 was employed. The bottommost portion is a substrate 1304. Anoptional intermediate layer(s) 1308 may be deposited upon the substrate1304. A photoresist pattern 1312 is on the optional intermediatelayer(s) 1308. A clear protective coating 1316 envelopes the photoresist1312.

With reference to FIG. 14, a flow diagram of another embodiment of aprocess for lithographing text and/or graphics onto a semiconductorsubstrate is shown. The process begins in step 1400 where one or morelayers of materials such as metals or polysilicons are deposited on thesubstrate. Next, photoresist is deposited in step 1410. In step 1420,the photoresist is exposed to electromagnetic radiation of theappropriate wavelength through the mask.

Etch away the exposed or unexposed photoresist to leave a positive ornegative impression in step 1430. The layer below the photoresist isetched through the cavities created in the photoresist layer in step1440. Any photoresist left behind is removed to reveal the patternedlayer of material in step 1450. Optionally, coat the wafer with anoptically clear protective material in step 1460.

Referring next to FIG. 15, a side elevational view of another embodimentof a semiconductor wafer 1500 with text and/or graphics lithographedthereon is shown. To produce the semiconductor wafer 1500 depicted, theprocess of FIG. 14 was employed. The bottommost portion is a substrate1504. An optional intermediate layer(s) 1508 may be deposited upon thesubstrate 1504. A metal pattern 1512 is on the optional intermediatelayer(s) 1508. A clear protective coating 1516 envelopes the metalpattern 1512.

With reference to FIG. 16, a flow diagram of yet another embodiment of aprocess for lithographing text and/or graphics onto a semiconductorsubstrate is shown. The process begins in step 1600 where photoresist isdeposited directly on the substrate or on a layer of some other materialthat has first been deposited on the substrate. In step 1610, thephotoresist is exposed to electromagnetic radiation of the appropriatewavelength through the mask. The exposed or unexposed photoresist isetched away in step 1620 to leave a positive or negative impression.Next, a material such as a metal or a polysilicon is deposited on thepatterned photoresist in step 1630. The photoresist is lifted off instep 1640 leaving behind the material from step 1630 in the cavities ofthe photoresist pattern. Optionally, the wafer is coated with anoptically clear protective material in step 1650.

Referring next to FIG. 17, is a side elevational view of yet anotherembodiment of a semiconductor wafer with text and/or graphicslithographed thereon is shown. To produce the semiconductor wafer 1700depicted, the process of FIG. 16 was employed. The bottommost portion isa substrate 1704. An optional intermediate layer(s) 1708 may bedeposited upon the substrate 1704. A metal pattern 1712 is on theoptional intermediate layer(s) 1708. A clear protective coating 1716envelopes the metal pattern 1712.

The information stored in text and graphics may be accessed. Amagnification device equipped with an illuminator that can cast light onthe chip from above can be used to aid the human eye to see the finedetails of the information on the chip. The chip can be mounted on astage capable of precise movements under the magnifying device. Themagnification device may be coupled to an electronic or photographiccapture device, such as a film camera or an electronic camera.

If the chip is imaged by the magnification device and captured by anelectronic capture device, the resulting electronic image may beprocessed. For instance, one could compare the electronic images of twochips to see if they are identical. This capability could be used foraccess control or security applications. One could also performautomated character recognition. The output could be printed, searchedfor specific items or translated into an audio signal and transmitted sothat the chip could be “read out loud” to a human or a listening device.

In light of the above description, a number of advantages of the presentinvention are readily apparent. First, the density of informationstorage can be very high. This is due to the very small features thatcan be fabricated with modern VLSI technology. Second, the informationstorage is very durable against disruptive influences such asradioactivity, strong electromagnetic fields, high temperatures,moisture, chemicals and mechanical strain. Existing means of informationstorage, such as magnetic discs, tapes and CDs tend to fall prey to oneor more of these factors. In fact, even electronic memories fabricatedusing VLSI technology can not robustly tolerate these influences. Third,information access from our devices is straightforward. Finally, thismeans of information storage is very cost effective and easy tomanufacture in large quantities.

A number of variations and modifications of the invention can also beused. For example, the substrates used could be an insulator. The layerscould be formed over the insulator using VLSI techniques.

Although the invention is described with reference to specificembodiments thereof, the embodiments are merely illustrative, and notlimiting, of the invention, the scope of which is to be determinedsolely by the appended claims.

1. A die with text deposited upon the die using semiconductor processingtechniques, the die comprising: a substrate which is cut from asemiconductor wafer comprising a plurality of substrates; a firstparagraph in contact with the substrate; and a second paragraph incontact with the substrate and aligned with the first paragraph in acolumn.
 2. The die with text deposited upon the die using semiconductorprocessing techniques of claim 1, wherein: the substrate is asemiconductor substrate; and text in the column is comprised of one ormore of a metal, an oxide, a polysemiconductor and a photoresist.
 3. Thedie with text deposited upon the die using semiconductor processingtechniques of claim 1, wherein the first and second paragraphs arecomprised of a plurality of characters.
 4. The die with text depositedupon the die using semiconductor processing techniques of claim 3,wherein each of the plurality of characters is comprised of a pluralityof primitives.
 5. The die with text deposited upon the die usingsemiconductor processing techniques of claim 1, the die furthercomprising: a first character appearing in a first color; and a secondcharacter appearing in a second color.
 6. The die with text depositedupon the die using semiconductor processing techniques of claim 1, thedie further comprising an image on the substrate.
 7. The die with textdeposited upon the die using semiconductor processing techniques ofclaim 1, the die further comprising a third paragraph on the substrate,wherein the second and third paragraphs are arranged in two columns onthe substrate.
 8. The die with text deposited upon the die usingsemiconductor processing techniques of claim 1, further comprising asilhouette image in contact with the substrate and at least partiallyoverlapping with at least one of the first or second paragraphs.
 9. Adie with information deposited upon the die using semiconductorprocessing techniques, the die comprising: a substrate which is cut froma semiconductor wafer comprising a plurality of substrates; a firstparagraph deposited upon the substrate; and a second paragraph depositedupon the substrate and aligned with the first paragraph in one or morecolumns.
 10. The die with information deposited upon the die usingsemiconductor processing techniques of claim 9, wherein the firstparagraph is derived from an electronic file that comprises a pluralityof elements corresponding to characters for the first paragraphs. 11.The die with information deposited upon the die using semiconductorprocessing techniques of claim 10, wherein each character of the firstand second paragraphs is comprised of a plurality of rectangles whereinone side of the rectangle is equal in size to the process resolution.12. The die with information deposited upon the die using semiconductorprocessing techniques of claim 9, wherein the first and secondparagraphs are separated by at least one of: a hard return, a tab or anenlarged character.
 13. The die with information deposited upon the dieusing semiconductor processing techniques of claim 9, the die furthercomprising: a first character visible as a first color; and a secondcharacter visible as a second color, which is different from the first.14. The die with information deposited upon the die using semiconductorprocessing techniques of claim 9, further comprising a silhouette imagein contact with the substrate and at least partially overlapping with atleast one of the first or second paragraphs.
 15. The die withinformation deposited upon the die using semiconductor processingtechniques of claim 9, wherein the first paragraph is deposited using alithographic technique that includes a mask.
 16. The die withinformation deposited upon the die using semiconductor processingtechniques of claim 9, wherein the first paragraph is produced with amethod comprising steps of: converting a first character of the firstparagraph into a first pattern; converting a second character of thefirst paragraph into a second pattern; and aligning the first and secondcharacters on a line.
 17. The die with information deposited upon thedie using semiconductor processing techniques of claim 9, wherein thefirst paragraph is produced with a method comprising a step ofdetermining an end of a first line and beginning a second line.
 18. Thedie with information deposited upon the die using semiconductorprocessing techniques of claim 9, wherein the column is produced with amethod comprising a step of determining an end of the first paragraphand beginning the second paragraph on the next line of the column. 19.The die with information deposited upon the die using semiconductorprocessing techniques of claim 9, wherein the column is produced with amethod comprising a step of detecting an end of a first column anddepositing a next line in a second column.
 20. The die with informationdeposited upon the die using semiconductor processing techniques ofclaim 9, wherein the first paragraph is produced with a methodcomprising steps of: determining a first color for a first character;and determining a second color for a second character.
 21. A die withinformation deposited upon the die using semiconductor processingtechniques, the die comprising: a substrate which is cut from asemiconductor wafer comprising a plurality of substrates arranged in agrid of the semiconductor wafer; a paragraph photolithographicallydeposited upon the substrate; and a silhouette image in contact with thesubstrate and at least partially overlapping with the paragraph.
 22. Thedie with information deposited upon the die using semiconductorprocessing techniques of claim 21, wherein the paragraph is derived froman electronic file that comprises a plurality of elements correspondingto characters for the paragraphs.
 23. The die with information depositedupon the die using semiconductor processing techniques of claim 21,wherein each character of the paragraph is comprised of a plurality ofrectangles wherein one side of the rectangle is equal in size to theprocess resolution.
 24. The die with information deposited upon the dieusing semiconductor processing techniques of claim 21, the die furthercomprising: a first character visible as a first color; and a secondcharacter visible as a second color, which is different from the first.25. The die with information deposited upon the die using semiconductorprocessing techniques of claim 21, wherein the paragraph is depositedusing a lithographic technique that includes a mask.
 26. A die withinformation deposited upon the die using semiconductor processingtechniques, the die comprising: a substrate which is cut from asemiconductor wafer comprising a plurality of substrates arranged in agrid of the semiconductor wafer; a first paragraph photolithographicallydeposited upon the substrate; a second paragraph photolithographicallydeposited upon the substrate; and a silhouette image in contact with thesubstrate and at least partially overlapping at least one of the firstor second paragraphs.
 27. The die with information deposited upon thedie using semiconductor processing techniques of claim 26, the diefurther comprising: a first character visible as a first color; and asecond character visible as a second color, which is different from thefirst.
 28. The die with information deposited upon the die usingsemiconductor processing techniques of claim 26, wherein the firstparagraph is deposited using a lithographic technique that includes amask.
 29. A die with information deposited upon the die usingsemiconductor processing techniques, the die comprising: a substratewhich is cut from a semiconductor wafer comprising a plurality ofsubstrates arranged in a grid of the semiconductor wafer; a firstparagraph photolithographically deposited upon the substrate; a secondparagraph photolithographically deposited upon the substrate wherein atleast one of the first or second paragraphs is generated with anelectronic file and wherein the first and second paragraphs arecomprised of a plurality of characters; and a silhouette image incontact with the substrate and at least partially overlapping at leastone of the first or second paragraphs.